Replace matrix @ vector list comprehensions with something more efficient
Quickest way AFAIK:

mat = np.array(self.curveObj.matrix_world)

verts_co = np.zeros((vertCount*3), dtype=np.float)
mesh.vertices.foreach_get("co", verts_co)
verts_co.shape = (vertCount, 3)
verts_co_4d = np.ones(shape=(vertCount, 4), dtype=np.float)
verts_co_4d[:, :-1] = verts_co  # cos v (x,y,z,1) - point,   v(x,y,z,0)- vector
splinePoints_world = np.einsum('ij,aj-&gt;ai', mat, splinePoints)